In a wireless telecommunication network, MIMO (multiple-input multiple-output) technology improves the communication ability due to the use of multiple antennas at both the wireless sender and receiver. In the MIMO technology, the more mature SU-MIMO (Single User multiple-input multiple-output) enables the time-frequency resources of the BS (Base Station) to an one-to-one correspondence with that of the MS (Mobile Station), and the BS communicates with single MS at a specific time-frequency resource via multiple antennas; therefore, the communication ability between the BS and the single MS are greatly improved. However, with the increment of the number of the MSs, the situation that multiple MSs share common time-frequency resources for communication should be considered; therefore, Multiple-User MIMO (MU-MIMO) obtains wide attention and study. In MU-MIMO, the BS communicates with multiple different MSs at the same time-frequency resource simultaneously via multiple antennas; therefore, the communication ability among the BS and multiple MSs can be improved simultaneously.
In the existing SU-MIMO and MU-MIMO, most studies are limited to the situation that the BS uses its own antennas to communicate with single MS or mu MSs. However, in a wireless Mesh network or wireless self-organized network, if the MIMO communication of the MS can He performed simultaneously and coordinately by the BS of its own cell and other neighbouring BSs with good communication quality, then the communication ability of the MS can be improved compared with single BS service. Therefore, the multiple-BS collaborative MIMO(CO-MIMO) has received a lot of attention. To be specific, multiple-BS CO-MIMO uses multiple antennas of the serving BS and the coordinating BS with different geographic locations, to coordinately perform MIMO communication with the MS.
In multiple-BS CO-MIMO, it is a necessary step of determining precoding information according to the channel information between the serving BS and the MS, and between the coordinating BS and the MS. In Time Division Duplex (TDD) mode where the channel reciprocity between the downlink and the uplink holds, the serving BS and coordinating BS can obtain the uplink channel responses between the serving BS and the MS, and between the coordinating BS and the MS according to the uplink from the MS, and calculate the downlink channel information between the serving BS and the MS, and between the coordinating BS and the MS respectively, and each corresponding downlink precoding matrix, according to the uplink channel response. However, in frequency-division duplex (FDD) mode, because the frequency difference between downlink and uplink carrier usually exceeds the channel coherent bandwidth, the downlink channel fading is almost uncorrelated with the uplink one in most cases, which results that the serving and coordinating BSs can not determine their respective downlink channel information according to uplink channel fading. Further, the serving BS and toe coordinating BS can not determine their corresponding downlink precoding matrix, therefore, the CO-MIMO downlink data communication with the MS can not be implemented. There is no method for effectively solving this problem in the prior art.